Wind turbine operational method

Abstract

Operation method for a variable speed wind turbine which comprises control methods for blade pitch in cases of extreme gusts of wind, characterized by the fact that it is comprised of the following steps: a) detection of the presence of an extreme gust of wind; b) performance of a sudden increase in pitch within the range of 6 to 14 degrees at the maximum speed permitted by the wind turbine blade pitch control mechanisms. The method also includes an additional step; c) vary the generator speed to avoid an increased acceleration of the generator which could make a subsequent step b) necessary.

1. A method for the operation of a variable-speed wind turbine having pitch control means in cases of an extreme operating wind gust, wherein the method comprises the steps of:
 a) detecting the presence of an extreme operating wind gust according to the generator acceleration when the generator acceleration is higher than a predetermined value in the range of 10% to 30% of the generator nominal acceleration, GNS/sec, during a minimum predetermined period of time in the range of 0.2 sec to 0.6 sec; and 
 b) performing a sudden increase of the pitch angle in the range of 6 to 14 degrees at the maximum pitch rate allowed by the wind turbine pitch control means. 
 
     
     
       2. A method for the operation of a variable-speed wind turbine according to  claim 1 , wherein said predetermined generator acceleration value is 20% of the generator nominal acceleration, GNS/sec. 
     
     
       3. A method for the operation of a variable-speed wind turbine according to  claim 1 , wherein said minimum predetermined period of time is 0.4 seconds. 
     
     
       4. A method for the operation of a variable-speed wind turbine according to  claim 1 , wherein the magnitude of said increase of the pitch angle is in the range of 12-14 degrees. 
     
     
       5. A method for the operation of a variable-speed wind turbine according to  claim 1 , further comprising the step of:
 c) varying the generator speed to avoid large generator accelerations that may result in the need for a subsequent step b). 
 
     
     
       6. A method for the operation of a variable-speed wind turbine according to  claim 5 , wherein step c) includes the following sub-steps:
 c1) decreasing the generator speed at a rate in the range of 1% to 4% of the generator nominal acceleration, GNS/sec, up to reach a generator speed value in the range of 60% to 90% of the generator nominal speed, GNS; and 
 c2) increasing the generator speed at a rate in the range of 0.5% to 2% of the generator nominal acceleration, GNS/sec, up to reach the generator nominal speed. 
 
     
     
       7. A method for the operation of a variable-speed wind turbine according to  claim 6 , wherein said generator speed decreasing rate is 2% of the generator nominal acceleration, GNS/sec. 
     
     
       8. A method for the operation of a variable-speed wind turbine according to  claim 6 , wherein said generator speed value is 80% of the generator nominal speed, GNS. 
     
     
       9. A method for the operation of a variable-speed wind turbine according to  claim 6 , wherein said generator speed increasing rate is 1% of the generator nominal acceleration, GNS/sec.